Pipe perforating apparatus and method

ABSTRACT

A method and apparatus for perforating pipe from its interior, and in particular for perforating plastic well casing in situ. A linear actuator drives a claw-shaped bit. Linear motion of the cylinder is converted to a pivoting of the bit in a radial direction by a deflector. In a preferred embodiment, the linear actuator is a hydraulic piston-cylinder assembly and the deflector is an inclined surface. Operation of the actuator in a first direction drives the bit into the inclined deflection surface, which causes the bit to pivot and protract radially outward of the tool housing to perforate the wall of a pipe. Operation of the actuator in the opposite direction pulls the bit back into the tool housing so that the perforator tool can be easily moved with a well casing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to perforating pipe, and in particular to perforating plastic pipe well casings in situ.

2. Background Art

Decomposition in waste landfills, particularly in the hot and humid gulf coast region, creates methane gas. Accordingly, wells are drilled in landfills for the production of methane gas. Landfill gas wells are typically made of high density polyethylene (HDPE) or polyvinyl chloride (PVC) pipe.

As waste is added to a landfill on top of existing well field, the voids within the lower gas-producing region are compressed and the water levels are raised, which results in a reduced radius of influence and more difficult gas extraction. Typically, landfill addition has required the costly re-drilling of new wells to maintain adequate gas extraction rates.

It is therefore advantageous to be able to perforate existing gas wells in situ to raise the production zones as the landfill builds. Such ability provides for a longer useful life for existing gas wells, thus reducing the cost of methane production.

Some perforator tools are known in the art, but the perforations created by these devices have typically been small. As a result, these small perforations tend to close up, or “self-heal,” particularly in HDPE pipe. Perforators which create large openings have typically been too slow and inefficient for satisfactory use.

3. Identification of Objects of the Invention

A primary object of the invention is to provide a method and apparatus for efficiently making large perforations in plastic well pipe from the inside of the pipe.

Another object of the invention is to provide a perforating apparatus that is easily run down serpentine wells and a method for moving the perforating apparatus past potential choke points.

SUMMARY OF THE INVENTION

The objects described above and other advantages and features of the invention are incorporated in a method and a well perforator system that provides for simple and effective puncturing of plastic well casing in situ. A linear actuator drives a claw-shaped bit. Linear motion of the cylinder is converted to a pivoting of the bit in a radial direction by a deflector. In a preferred embodiment, the linear actuator is a hydraulic piston-cylinder assembly and the deflector is an inclined surface. Operation of the actuator in a first direction drives the bit into the inclined deflection surface, which causes the bit to pivot and protract radially outward of the tool housing to perforate the wall of a pipe. Operation of the actuator in the opposite direction pulls the bit back into the tool housing so that the perforator tool can be easily moved with a well casing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail hereinafter on the basis of the embodiments represented in the accompanying figures, in which:

FIG. 1 is an elevation view of a well perforator system according to a preferred embodiment of the invention, showing a conventional skid steer vehicle equipped with a small drawworks unit and a downhole perforator tool for deployment into existing well bores;

FIG. 2 is an elevational view in partial cross-section of the well perforator system of FIG. 1 with the perforator tool deployed into a well bore, showing a perforating claw protracted to puncture the well casing;

FIG. 3A is an exploded side view in partial cross-section of the upper assembly of the perforator tool of FIGS. 1 and 2, showing an upper housing, a hydraulic cylinder assembly, and a claw assembly;

FIG. 3B is an exploded side view of the complete perforator tool of FIGS. 1 and 2, showing an assembled upper portion according to FIG. 3A and a lower housing;

FIG. 4A is a front elevational view in partial cross-section of the downhole perforator tool of FIGS. 1-3B, showing a slot formed within the lower housing through which a perforating claw protracts and retracts and a ‘U’-shaped gudgeon or clevis that pivotally connects the perforating claw to a hydraulic cylinder assembly;

FIG. 4B is a top view of the downhole perforator tool of FIG. 4A taken along lines 4B-4B of FIG. 4A;

FIG. 4C is a cross-sectional view of the downhole perforator tool of FIG. 4A taken along lines 4C-4C of FIG. 4A;

FIG. 4D is a cross-sectional view of the downhole perforator tool of FIG. 4A taken along lines 4D-4D of FIG. 4A;

FIG. 4E is a cross-sectional view of the downhole perforating tool of FIG. 4A taken along lines 4E-4E of FIG. 4A;

FIG. 5A is a side view in partial cross-section of the downhole perforator tool of FIGS. 1-4E showing the perforating claw in the fully retracted position; and

FIG. 5B is a side view in partial cross section of the downhole perforator tool of FIG. 5A, showing the perforating claw in the fully protracted position.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 illustrates a well perforator system 10 according to a preferred embodiment of the invention. A skid-mounted drawworks unit 12 is carried by a conventional skid steer vehicle 14 for conveniently transporting the perforator system 10 from well to well in a landfill, for example. Drawworks unit 12 is mounted on a skid, pallet or the like 20 and includes a raised arm 22 that carries a block 24. A winch 26 is mounted to skid 20 and carries a wire rope or chain 28, which is passed over a sheave in block 24. The bitter end of wire rope 28 carries a downhole perforator tool 100, which is run into and out of well casings by winch 26. A flexible conduit 30 supplies perforator tool 100 with power for perforating well casing.

Preferably, perforator tool 100 is hydraulically powered, in which case conduit 30 consists of a pair of hydraulic hoses—one for fluid supply and the other for fluid return. However, electric, pneumatic, or other mechanical power may be used in place of hydraulic power as appropriate.

A local source of hydraulic power, such as a gasoline engine driving a hydraulic pump, may be included with drawworks unit 12 for powering tool 100 via hoses 30. Alternatively, hydraulic power may be provided by skid steer vehicle 14, from a power take-off (PTO) unit, for example. FIG. 1 shows hoses 32 connected between drawworks unit 12 and skid steer 14.

FIG. 2 illustrates perforator system 10 in use in a typical application. An existing well 50 has a bore that is lined with HDPE casing 52, for example. As a lower zone of production 54 experiences diminished production due to compression of voids and rising water level under the influence of increased landfill buildup, a new zone of production 56 is created at a higher elevation. Perforator tool 100 is lowered into well 50 to an elevation that corresponds with new zone 56. Pressurized hydraulic fluid is supplied to tool 100 in a direction to cause a claw-shaped bit 102 to protract outwardly from the housing 104 of tool 100. Claw 102 is forced through the HDPE casing 52, creating a large non-self-healing hole therethrough. Claw 102 is then retracted into housing 104 by reversing the hydraulic fluid flow. Perforator tool 100 is then free to be raised, lowered, and/or rotated into a new position for creating another perforation, and so on.

Tool 100 is generally cylindrically shaped and has an outer diameter to allow tool 100 to pass freely through casing 52 when its perforating claw is fully retracted. However, the dimensions of tool 100 are such that when its perforating claw 102 is fully protracted, its width exceeds the inner diameter of casing 52. For example, for a six inch well bore, tool 100 preferably has housing 104 with about a 4-5 inch outer diameter. When fully protracted, claw 102 extends about 2-3 inches beyond housing 104.

The dimension of tool housing 104 is preferably small enough to allow tool 100 to be easily passed through most well bores. However, well bores are often serpentine in nature, and they can become somewhat crushed and oblong in certain locations. If tool 100 becomes lodged when lowering it, claw 102 can be repeatedly cycled between fully-retracted and half-protracted positions. Each cycle causes the claw to engage the well casing and pull tool downward slightly. Repetitive cycling tends to “walk” tool 100 below problematic spots in the well bore.

Referring now to FIGS. 3A and 3B, exploded assembly diagrams of downhole perforator tool 100 are provided. FIG. 3A illustrates the assembly of the upper tool assembly 110. A hollow cylindrical upper housing 112 includes a circular internal base plate 114. Upper housing 112 and base plate 114 are ideally made of steel, and base plate 114 is attached inside upper housing 112 near its lower end by welding. Base plate 114 includes a hole 116 positioned at its center for accommodating the piston rod 132 of a hydraulic cylinder assembly 130. Base plate 114 also includes four threaded holes 118 (indicated by hidden line) spaced at ninety degree intervals about the center of base plate 114 near its perimeter.

Hydraulic cylinder assembly 130 has a generally square profile, although a cylinder assembly with a circular profile may be used as well. Cylinder assembly 130 is dimensioned to fit snugly within upper housing 112, with the rod end 134 abutting the upper surface of base plate 114. Cylinder assembly 130 includes four bores 136 formed through its longitudinal length, which are spaced at ninety degree intervals about the centerline of piston rod 132 and at the same spacing as threaded holes 118 of base plate 114. Cylinder assembly 130 includes inlet and outlet fluid ports 138, 139, and upper housing 112 includes one or more recesses, slots or openings 113 that are positioned so that ports 138 and 139 can be accessed.

Upper tool assembly 100 includes an end cap 140. End cap 140 is preferably formed of steel plate and has a generally circular shape that is dimensioned to fit snugly within upper housing 112. End cap 140 includes four holes 142 spaced ninety degrees about its center at the same spacing as cylinder assembly bores 136 and threaded base plate holes 118. End cap 140 also preferably includes a padeye 144 for securing downhole tool 100 to chain or wire rope 28 with a shackle 29 (FIG. 1).

Finally, upper tool assembly 110 includes a claw assembly 150, which preferably includes a perforating bit 102 pivotally mounted to a ‘U’-shaped clevis or gudgeon 152, with a pintle, pin or bolt 154, for example. Bit 102 may be journaled to gudgeon 152 with a ball bearing assembly, or the like, if desired. Clevis or gudgeon 152 is adapted to be connected to the end of piston rod 132. Preferably, a threaded connection is used, which allows fine length adjustment of upper tool assembly 110.

Perforating bit 102 is a planar member having the general shape of an apostrophe or claw. The larger round end of claw 102 defines a crosshead 156 and includes a hole formed therethrough for receiving bolt 154. The distal end of claw 102 forms a sharp tip 157. A convex side 158 and a concave side 159 are defined between tip 157 and crosshead 156.

Upper tool assembly 110 is assembled as follows: Bores 136 of cylinder assembly 130 are aligned with threaded holes 118 of base plate 114, and cylinder assembly 130 is inserted into upper housing 112 until its rod end 134 rests on base plate 114 with piston rod 132 extending through hole 116. Next, end cap 140 is oriented so that holes 142 align with bores 136 and is inserted into upper housing 112 above cylinder assembly 130. The longitudinal dimension of upper housing 112 and cylinder assembly 130 are such that end cap 140 fits flush with the upper end of upper housing 112 and snuggly encases cylinder assembly 130. Four threaded fasteners 148 are passed through holes 142 in end cap 140 and bores 136 in cylinder 130. Fasteners 148 are threaded into holes 118 in base plate 114. Finally, claw assembly 150 is connected by threading or otherwise attaching gudgeon 152 to piston rod 132.

In FIG. 3B, the final assembly of perforator tool 100 is illustrated. Upper tool assembly 110, as described above with reference to FIG. 3A, is mated to a lower housing 160. Lower housing 160 is a hollow cylinder of the same diameter of upper housing 112, preferably made of steel, with an inclined or tapered lower end. An oval-shaped steel plate 162 is welded to the cylindrical walls of lower housing 160 to form a closed lower end. The upper end of lower housing 160 has male threads 164, which mate with female threads 119 formed in the lower end of upper housing 112. However, an opposite thread configuration, in which the lower housing has female threads and the upper housing has male threads, is possible. Upper housing 112, end cap 140, and lower housing 160 (including inclined plate 162) collectively comprise perforator tool housing 104 (FIG. 1).

FIG. 4A is a front elevation view of perforator tool 100, with a small portion of lower housing 160 cut away to reveal detail of claw 102 and gudgeon 152. Lower housing 160 has a longitudinal slot 166 formed therein centered at the lowest point 167 of housing 160. Slot 166 allows claw tip 157 to protract from and retract into housing 104. The interior side of inclined plate 162 ideally has a concave groove 168 formed therein (best seen in FIGS. 5A and 5B) that accommodates and guides convex edge 158 of claw 102 during protraction and retraction of the claw.

FIG. 4A shows downhole perforator tool 100 equipped with ninety degree elbow fittings 34 at ports 138 and 139 of cylinder assembly 130 for connecting to hydraulic hoses 30 (FIG. 1). Slot 113 provides clearance for locating short lengths of rigid tubing 36 (FIG. 1) alongside cylinder 130 so the tubing 36 does not protrude beyond housing 104. Rigid tubing 36 connects to the flexible hydraulic hoses 30 above perforator tool 100 (see FIG. 1). In this manner, damage to the hydraulic connections from contact with well casing 52 (FIG. 2) is prevented.

FIG. 4B is a plan view of perforator tool 100 from the vantage point of lines 4B-4B of FIG. 4A. End cap 140 includes a small cutout 141, which provides room for rigid hydraulic tubing 36 to pass without extending beyond the circumference of housing 104.

FIGS. 4C-4E are cross-sections taken along the lines indicated in FIG. 4A. These figures provide clarification about the structure of hydraulic cylinder assembly 130 and how it fits within upper housing 112 and relates to slot 113.

The operation of downhole perforator tool 100 is described with reference to FIGS. 5A and 5B. FIG. 5A is a side view of tool 100 in partial cross-section taken along lines 5A-5A of FIG. 4A. FIG. 5A shows claw 102 in the fully retracted position. FIG. 5B is a view that is identical to FIG. 5A, except that claw 102 is fully protracted.

Referring to FIG. 5A, in order to protract claw 102 for perforating a well casing 52 (FIG. 2), hydraulic fluid is pumped into upper port 138 of hydraulic cylinder assembly 130. Hydraulic cylinder assembly includes a piston 133 that is dynamically sealed against the internal cylinder walls 135. An unbalanced pressure across piston 133 causes it to slide within cylinder 130 as is well known in the art. Accordingly, by pumping fluid under pressure into port 138, piston 133 moves downward and applies a large downward force on claw 102 via piston rod 132, gudgeon 152 and bolt 154. As claw 102 attempts to move in a downward direction, it is deflected by inclined plate 162 so that it pivots about bolt 154, thus causing claw tip 157 to pass through slot 166 to puncture the wall of well casing 52 (FIG. 2). The convex side 158 of claw 102 and the concave groove 168 in inclined plate 162 cooperate to provide a smooth pivoting deflection.

To retract claw 102, pressurized fluid is pumped into lower port 139, which raises piston 133, piston rod 132, gudgeon 152, and claw crosshead 156. When raised, claw 102 pivots about bolt 154 and retracts into housing 104.

Although an embodiment using a single claw-shaped bit is described herein, multiple bits may be used as appropriate within the scope of the invention. Similarly, although the means for deflecting the puncturing bit is described as an inclined surface, alternative deflectors may be used, such as a bellcrank, for example, within the scope of the invention.

The Abstract of the disclosure is written solely for providing the United States Patent and Trademark Office and the public at large with a way by which to determine quickly from a cursory reading the nature and gist of the technical disclosure, and it represents solely a preferred embodiment and is not indicative of the nature of the invention as a whole.

While some embodiments of the invention have been illustrated in detail, the invention is not limited to the embodiments shown; modifications and adaptations of the above embodiment may occur to those skilled in the art. Such modifications and adaptations are in the spirit and scope of the invention as set forth herein: 

1. A tool (100) for perforating a pipe (52) from the interior of the pipe, said tool defining a longitudinal axis, the tool comprising: an actuator (130) operable to reciprocate a gudgeon (152); and a bit (102) having a first end (156) pivotally coupled to said gudgeon and a second end (157) defining a claw; whereby movement of said gudgeon in a first direction causes pivotal protraction of said claw outward from said axis.
 2. The tool of claim 1 wherein: said first end of said bit defines a crosshead that is journaled to said gudgeon.
 3. The tool of claim 1 further comprising: a deflector (162) disposed at a fixed distance from said actuator; whereby linear movement of said gudgeon in said first direction is converted by said deflector to pivotal protraction of said claw radially outward from said axis.
 4. The tool of claim 1 further comprising: a housing (104) enclosing said actuator and said gudgeon, said housing having an opening (166); whereby translation of said gudgeon by said actuator in said first direction forcibly protracts said claw through said opening a distance beyond said housing, and translation of said gudgeon by said actuator in a second direction opposite to said first direction retracts said claw into said housing.
 5. The tool of claim 1 further comprising: a generally cylindrical housing (104) enclosing said actuator and said gudgeon, said housing being centered about said axis and having top and bottom ends (140, 162), said bottom end (162) of said housing being inclined at an acute angle with respect to said axis; whereby translation of said gudgeon by said actuator toward said bottom end of said housing causes said bit to contact and deflect off an inclined interior surface of said bottom end for pivoting said bit about said gudgeon.
 6. The tool of claim 1 wherein: said actuator is a cylinder-piston assembly.
 7. The tool of claim 1 wherein: said claw of said bit is generally planar having first and second parallel sides, a third convex side (158) and a fourth concave side (159).
 8. The tool of claim 1 wherein: only a single bit is present.
 9. The tool of claim 1 further comprising: a drawworks (12) carrying a tension member (28), said housing (104) carried by said tension member; and a vehicle (14) carrying said drawworks and providing power to said actuator.
 10. A method for perforating a pipe comprising the steps of: inserting a linear actuator (130) into said pipe (52); activating said actuator in a first direction to move a gudgeon (152) and a bit (102) attached to said actuator; and pivoting said bit so that a distal pointed end (150) of said bit is protracted through the wall of said pipe.
 11. The method of claim 10 further comprising the step of: activating said actuator in a second direction to retract said bit from said wall of said pipe.
 12. The method of claim 10 further comprising the step of: pivoting said bit by a deflector (162).
 13. The method of claim 12 wherein: said deflector is an inclined surface.
 14. The method of claim 13 wherein: said bit has a convex edge (158); and said inclined surface has a concave groove (168); whereby a contact force of said convex edge against said concave groove acts to pivot said bit. 